Patent Document 1 discloses a mist cooling apparatus which is used for the heat treatment on a treated subject such as metal so as to cool the treated subject. The mist cooling apparatus sprays a mist-like cooling liquid to the heated treated subject so as to cool the treated subject using the latent heat of vaporization of the cooling liquid. For this reason, the mist cooling apparatus has high cooling performance compared to a gas ejecting type cooling apparatus of the related art. Further, when the mist ejection amount or the mist ejection time is adjusted, the mist cooling apparatus may easily control cooling speed of the treated subject which is difficult to control in an immersion type cooling apparatus of the related art.